It has long been recognized that limiting the exposure of both humans and animals to toxic or carcinogenic substances in food, water, and air is critical to our survival. Of all the toxic or carcinogenic substances that can be encountered in the environment, aflatoxins are especially important, since the presence of even minute quantities of these fungal metabolites constitute a serious health hazard. Aflatoxins are polycyclic aromatic compounds that are found in foods such as grain and peanuts as a consequence of the manner in which the foods were grown, handled, or stored. A variety of aflatoxins, including B.sub.1, B.sub.2, G.sub.1, G.sub.2, M.sub.1, and M.sub.2, have been isolated and characterized. Aflatoxin B.sub.1 is the most biologically potent of these compounds, and, as well as being a potent toxin, is also a mutagen and carcinogen.
Since aflatoxins endanger public health, it is a common practice to run regular tests for aflatoxins on samples of certain foodstuffs. Such tests are typically conducted by extracting samples with an appropriate solvent, and then using standard techniques such as high pressure liquid chromatography (HPLC) to detect and quantitate aflatoxins. For example, the use of HPLC for analysis of aflatoxins in peanuts is described in U.S. Pat. No. 4,285,698.
Most samples contain numerous contaminants in addition to aflatoxins. These substances can interfere with the quantitative and qualitative detection of the toxins. Because of this, sample extracts need to undergo further processing to remove the interfering substances. Additional processing of sample extracts is usually accomplished by passing the extract through a special "cleanup" column, which retains the aflatoxins while allowing the interfering substances to pass through. The aflatoxins are then eluted from the column with the appropriate solvent to yield a purified extract which can be analyzed by HPLC, or some other means.
Sample cleanup is currently accomplished through the use of immunoaffinity columns, as described in U.S. Pat. Nos. 4,818,687 and 4,859,611. The immunoaffinity columns are prepared by immobilizing on a solid support antibodies that are specific to aflatoxins. Upon passing crude food extract through the column, the aflatoxins bind to the immobilized antibodies and are selectively retained. Some major drawbacks associated with the use of immunoaffinity columns include the high cost of preparation, limited shelf-life, and non-reusability. Additionally, the immunoaffinity columns cannot be used for the detection or cleanup of structurally related compounds such as phytoestrogens, which contaminate soy and soy-based products including infant formula, as well as feed products like alfalfa. This is significant, as there has been much recent concern regarding the methods of detecting and removing phytoestrogens from food sources due to their demonstrated estrogenic effects and potential for carcinogenicity.
Cyclodextrin polymers have also been employed to filter contaminants from samples, as described in U.S. Pat. Nos. 4,726,905, 4,274,985, and 4,357,468. The '905 patent discloses a cyclodextrin polymer capable of filtering polychlorinated biphenyl compounds. The '985 and '468 patents disclose cyclodextrin polymers that are capable of filtering nicotine, benzene, phenol, cresol, and tar. While the polymers disclosed in these patents remove aromatic compounds from samples, the size, complexity, and physical nature of the removed compounds significantly differ. This suggests that the polymers would be ineffective in aflatoxin or phytoestrogen cleanup. In fact, some cyclodextrin copolymers, such as .beta.-cyclodextrin/epichlorohydrin copolymer, do not retain aflatoxins or phytoestrogens.
Consequently, there remains a need for a compound that effectively removes aflatoxins and phytoestrogens from samples, is chemically stable, is less expensive than immunoaffinity columns to manufacture, and is reusable at least once. It is an object of the present invention to provide a compound that satisfies these criteria and, therefore, demonstrates significant utility for the cleanup of aflatoxin or phytoestrogen contaminated samples.
It is a further object of the present invention to provide a means of using such a compound to remove aflatoxins or phytoestrogens from a sample. It is another object of the present invention to provide a means of using such a compound to detect aflatoxins and phytoestrogens in a sample. It is yet another object of the present invention to provide a means of using such a compound to quantitate levels of aflatoxins or phytoestrogens in a sample.
These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.